Oxidative dissolution of silver nanoparticles by synthetic manganese dioxide investigated by synchrotron X-ray absorption spectroscopy
- 46 Downloads
Silver nanoparticles (AgNPs) are widely used in a variety of industrial and consumer applications and the disposal AgNP-containing materials is a potential source of environmental contamination. This study investigated the reaction of AgNPs with synthetic birnessite (δ-MnO2), a naturally-occurring MnO2 soil mineral shown in previous studies to oxidize both organic and inorganic dissolved species. The AgNPs used in this study ranged in size from 5 to 25 nm with an average particle diameter of 15.6 nm. Batch and kinetic reactions of MnO2-treated AgNP suspensions were studied by detecting AgNP oxidation to Ag+ using a combination of UV-Vis and microwave plasma atomic emission (MP-AES) spectrometries. Synchrotron K-edge X-ray absorption spectroscopy (XANES and EXAFS) was used to investigate the Ag oxidation state and structural characteristics of the reaction products. Oxidation of AgNP by MnO2 was detected in batch reactions showing an initial fast oxidation of AgNP to Ag+ (0–10 min) followed by a slower reaction (> 10 min) where Ag+ was removed by adsorption on MnO2 surfaces. XANES results confirmed that total AgNP oxidation by MnO2 occurred after 48 h when the Mn:Ag mole ratio treatment exceeded 5:1. The final AgNP oxidation product determined by EXAFS was Ag+ ion bound as a AgO4 tetrahedral structure in MnO2 interlayer cation exchange sites with Ag-O and Ag-Mn inter-atomic distances of 2.28 (± 0.02) and 3.88 (± 0.09) Å, respectively. This structure is in agreement with previous EXAFS studies of naturally-occurring Ag-bearing MnO2 mineral samples and represents one of many possible Ag+ binding sites on soil mineral surfaces.
KeywordsSilver nanoparticles AgNP Manganese dioxide Oxidation X-ray absorption spectroscopy Environmental contamination
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Brittle SW, Foose DP, O’Neil KA, Sikon JM, Johnson JK, Stahler AC, Ryan J, Higgins SR, Sizemore IE (2018) A Raman-based imaging method for characterizing the molecular adsorption and spatial distribution of silver nanoparticles on hydrated mineral surfaces. Environ Sci Technol 52(5):2854–2862. https://doi.org/10.1021/acs.est.7b04884 CrossRefGoogle Scholar
- Cotton AF, Wilkinson G (1988) Advanced inorganic chemistry, 5th edn. Wiley-Interscience, New York, pp 939–945Google Scholar
- Niessner FF (ed) (2010) Nanoparticles in the water cycle: properties. Springer, Analysis and Environmental RelevanceGoogle Scholar
- Hooda PS (2010) Trace elements in soils, John Wiley & Sons, Inc pp 515-549Google Scholar
- Lowry GV, Espinasse BP, Badireddy AR, Richardson CJ, Reinsch BC, Bryant LD, Bone AJ, Deonarine A, Chae S, Therezien M, Colman BP, Hsu-Kim H, Bernhardt ES, Matson CW, Wiesner MR (2012) Long-term transformation and fate of manufactured Ag nanoparticles in a simulated large scale freshwater emergent wetland. Environ Sci Technol 46(13):7027–7036. https://doi.org/10.1021/es204608d CrossRefGoogle Scholar
- McKenzie RM (1989) Manganese oxides and hydroxides. In: Dixon JB, Weed SB (eds) Minerals in soil environments, SSSA book series number 1, 2nd edn. Soil Science Society of America, Madison, pp 439–465Google Scholar
- Morris J, Willis J (2007) U.S. Environmental Protection Agency Nanotechnology White Paper. U.S. Environmental Protection Agency, Washington, DC February, 2007Google Scholar
- Newville M (2001) IFEFFIT: interactive XAFS analysis and FEFF fitting. J Synchrotron Radiat 8:324–332Google Scholar
- Zhang X, Miao W, Li C, Sun X, Wang K, Yanwei Ma Y (2015) Microwave-assisted rapid synthesis of birnessite-type MnO2 nanoparticles for high performance supercapacitor applications. Mater Res Bull 71:111–115. https://doi.org/10.1016/j.materresbull.2015.07.023 CrossRefGoogle Scholar